Light irradiation device and sample observation apparatus
A light irradiation device includes: a light source configured to output light having coherence; a light focusing element having a focusing axis and a non-focusing axis intersecting with the focusing axis and configured to focus the light on a focusing line so as to generate planar light; and an aperture mask having an opening part that limits a part of luminous fluxes of the light transmitted from the light source to the light focusing element. The opening part of the aperture mask has opening edges disposed to extend in a direction along the focusing axis of the light focusing element, and, in a case in which the opening edges are projected onto the focusing line, corresponding projected portions have linear spreads.
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The present disclosure relates to a light irradiation device and a sample observation apparatus.
BACKGROUND ARTAs one of methods for observing the inside of a sample having a three-dimensional stereoscopic structure such as a cell or the like, selective plane illumination microscopy (SPIM) is known. As a technology relating to such a technique, for example, there is a sample observation apparatus described in Patent Literature 1. The sample observation apparatus of this Patent Literature 1 is configured to include an irradiation optical system that irradiates a sample with planar light, a scanning unit that scans a sample for an irradiation face of planar light, and an imaging optical system that has an observation axis inclined with respect to the irradiation face and forms an image of observation light generated in a sample in accordance with irradiation of planar light. Then, a plurality of pieces of partial image data corresponding to a part of an optical image according to observation light formed as an image by the imaging optical system are acquired, and observation image data of a sample is generated on the basis of such partial image data.
CITATION LIST Patent Literature
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- [Patent Literature 1] Japanese Unexamined Patent Publication No. 2018-063292
For example, the planar light used in the sample observation apparatus described above is formed by focusing light emitted from a light source using a light focusing element such as a cylindrical lens or the like. In irradiation of planar light onto a sample, it is preferable to limit an irradiation range of the planar light by disposing an aperture mask on an optical path such that observation areas of the sample adjacent to each other are not irradiated with the planar light. However, coherent light, for example, such as laser light is light having coherence, and thus interference fringes due to diffraction on the edge of the aperture mask are generated, and there is concern that a radiation illuminance distribution of the planar light may become non-uniform.
The present disclosure is for solving the problems described above, and an object thereof is to provide a light irradiation device and a sample observation apparatus capable of outputting planar light having a uniform radiation illuminance distribution.
Solution to ProblemAccording to one aspect of the present disclosure, there is provided a light irradiation device including: a light source configured to output light having coherence; a light focusing element having a focusing axis and a non-focusing axis intersecting with the focusing axis and configured to focus the light on a focusing line so as to generate planar light; and an aperture mask having an opening part that limits a part of luminous fluxes of the light transmitted from the light source to the light focusing element, in which the opening part of the aperture mask has opening edges disposed to extend in a direction along the focusing axis of the light focusing element, and, in a case in which the opening edges are projected onto the focusing line, corresponding projected portions have linear spreads.
In this light irradiation device, in the opening part of the aperture mask, in a case in which the opening edges disposed to extend in a direction along the focusing axis of the light focusing element are projected onto the focusing line, corresponding projected portions have linear spreads. In an aperture mask in which a corresponding projected portion is punctiform in a case in which the opening edges are projected onto the focusing line, interference fringes due to diffraction in the opening edges are mutually strengthened, and a radiation illuminance distribution of planar light tends to be non-uniform. In contrast to this, in an aperture mask in which the corresponding projected portions have linear spreads, interference fringes due to diffraction in the opening edges are not strengthened together, and the radiation illuminance distribution of the planar light can be uniformized. Thus, this light irradiation device can output planar light having a uniform radiation illuminance distribution.
The opening part may have an asymmetrical shape with respect to the focusing line. In addition, the opening edges may have shapes protruding to an outer side with respect to the focusing line. The opening part may have a hexagonal shape. According to such a configuration, interference fringes due to diffraction in the opening edges are further suppressed, and the radiation illuminance distribution of the planar light is further uniformized.
The opening part may have a trapezoid shape. The opening edges may have a zigzag shape. The opening edges may have a shape protruding to an outer side of the focusing line. Also in such a configuration, interference fringes due to diffraction in the opening edges are further suppressed, and the radiation illuminance distribution of the planar light is further uniformized.
The opening part may have a quadrangle shape, and the opening edges may intersect with the focusing axis at a predetermined angle. Also in such a configuration, interference fringes due to diffraction in the opening edges are further suppressed, and the radiation illuminance distribution of the planar light is further uniformized.
The light source may be a light source that outputs laser light as the light. The laser light is light, from which high radiation illuminance can be acquired, but has high coherence, and interference fringes due to diffraction in edges of an aperture mask may be easily generated. Thus, by applying an aperture mask having the configuration described above to laser light, planar light having a uniform radiation illuminance distribution can be appropriately output.
According to one aspect of the present disclosure, there is provided a sample observation apparatus including: the light irradiation device described above; and a detection unit configured to detect observation light generated in a sample in accordance with irradiation of the planar light from the light irradiation device.
In this sample observation apparatus, interference fringes due to diffraction in the opening edges of the aperture mask are not strengthened together, and the radiation illuminance distribution of the planar light can be uniformized. Thus, in this sample observation apparatus, by irradiating a sample with planar light of which the radiation illuminance distribution is uniformized, observation of the sample can be performed with high accuracy.
Advantageous Effects of InventionAccording to the present disclosure, planar light having a uniform radiation illuminance distribution can be output.
Hereinafter, preferred embodiments of a light irradiation device and a sample observation apparatus according to one aspect of the present disclosure will be described in detail with reference to the drawings.
As illustrated in
The scanning unit 4 is a mechanism that scans a sample S for the irradiation surface R of the planar light L1. In this embodiment, the scanning unit 4 is configured using a moving stage 12 that moves a sample container 11 storing a sample S. For example, the sample container 11 is a micro plate, a slide glass, a Petri dish, or the like. In this embodiment, a micro plate will be illustrated as an example. In the sample container 11, a plurality of wells 13 in which samples S are disposed are aligned, for example, in a linear shape (or a matrix shape). The sample container 11 may be fixed with respect to the moving stage 12. A bottom face of the well 13 serves as an input face of planar light L1 for a sample S disposed inside the well 13. The sample container 11 is disposed with respect to the moving stage 12 such that this input face is orthogonal to the optical axis P1 of the planar light L1.
As illustrated in
The imaging optical system 5 is an optical system that forms an image of the observation light L2 generated in the sample S in accordance with the irradiation of the planar light L1. For example, the imaging optical system 5 is configured to include an objective lens, an imaging lens, and the like. An optical axis of the imaging optical system 5 is an observation axis P2 of the observation light L2. In the example illustrated in
The image acquiring unit 6 is a part that detects observation light L2 formed as an image by the imaging optical system 5. For example, the image acquiring unit 6 is configured to include an imaging device that captures an optical image according to the observation light L2. Examples of the imaging device includes area image sensors such as a CMOS image sensor and a CCD image sensor. Such an area image sensor is disposed in the imaging surface according to the imaging optical system 5 and, for example, captures an optical image using a global shutter or a rolling shutter and outputs data of a two-dimensional image to the computer 7.
The computer 7, physically, is configured to include memories such as a RAM, a ROM, and the like, a processor (an arithmetic operation circuit) such as a CPU or the like, a communication interface, a storage unit such as a hard disk or the like, and a display unit such as a display or the like. Examples of the computer 7 include a personal computer, a cloud server, a smart device (a smartphone, a tablet terminal, or the like), and the like. The computer 7 executes a program stored in a memory using a CPU of the computer system, thereby functioning as a controller that controls operations of the light irradiation device 2 and the moving stage 12, an image generating unit that generates observation image data of a sample S, an analysis unit that analyzes the observation image data, and the like.
Next, the light irradiation device 2 described above will be described in more details.
The light focusing element 23, for example, is configured using a cylindrical lens, an axicon lens, a freeform lens, a spatial light modulator, or the like and is optically coupled with the light source 21. This light focusing element 23 has a focusing axis F1 and a non-focusing axis F2 that intersects with (here, orthogonal to) the focusing axis F1 and generates planar light L1 by focusing the light L0 that has passed through the opening part 24 on a focusing line K. In the example illustrated in
As illustrated in
Here, as described above, in a case in which an aperture mask is disposed on an optical path of coherent light such as laser light, generally, coherent light is light having strong coherence, and thus there is a problem in that interference fringes are generated in laser light after passage of an opening part due to diffraction in an opening edge of the aperture mask. This problem can similarly occur even in a case in which light passing through an opening part of the aperture mask is low coherent light. The interference fringes due to diffraction in the opening edge of the aperture mask overlap each other and are strengthened together when light is focused in a direction along a focusing axis by a light focusing element, and thus, it may be considered that a radiation illuminance distribution of planar light acquired by focusing light becomes non-uniform.
In the aperture mask 122 according to this comparative example, as illustrated in
On the other hand,
For example, the predetermined angle is equal to or larger than 1° and equal to or smaller than 5°. By configuring the predetermined angle to be equal to or larger than 1°, an effect of reduction of interference fringes can be sufficiently exhibited. In addition, by configuring the predetermined angle to be equal to or smaller than 5°, an excessive spread of an edge of the radiation illuminance distribution can be suppressed, and an area in which radiation illuminance is flat can be sufficiently secured. Relating to setting of an optimal predetermined angle, a length of the opening part 24A in the direction of the focusing axis F1 may be also considered.
In the aperture mask 22A according to this embodiment, as illustrated in
As described above, in the light irradiation device 2, in a case in which the opening edges 25A that are disposed to extend in a direction along the focusing axis F1 of the light focusing element 23 are projected onto the focusing line K in the opening part 24A of the aperture mask 22A, a corresponding projected portion P has a linear spread. In the aperture mask 22 of the comparative example in which a corresponding projected portion P is in a punctiform in a case in which the opening edges 25A are projected onto the focusing line K, interference fringes due to diffraction in the opening edges 25A are strengthened together, and the radiation illuminance distribution of the planar light L1 tends to be non-uniform. In contrast to this, in the aperture mask 22A according to the embodiment in which the corresponding projected portion P has a linear spread, interference fringes due to diffraction in the opening edges 25A are not strengthened together, and the radiation illuminance distribution of the planar light L1 can be uniformized. Thus, in this light irradiation device 2, the planar light L1 having a uniform radiation illuminance distribution can be output.
As a technology for suppressing interference fringes due to diffraction of light on the opening edge of an aperture mask, for example, there is a technique in which an optical filter called an apodizing filter or a soft aperture is disposed on an optical path. In addition, there is also a technique in which a diffraction component is suppressed by disposing an aspherical lens on an optical path instead of an optical filter. However, in such techniques, an optical element needs to be optimized in accordance with a wavelength or a beam diameter of used laser light, and, in a case in which laser light not matching characteristics of the optical element is used, there is concern that the effect of suppressing interference fringes due to diffraction of light on an opening edge may not be sufficiently exhibited.
In contrast to this, the light irradiation device 2 suppresses interference fringes due to diffraction of light L0 on the opening edges 25A using the configuration of the opening edges 25A of the aperture mask 22A. In this technique, an optical element does not need to be optimized in accordance with a wavelength or a beam diameter of used light L0, and operations/effects are acquired for various kinds of light L0. As in the sample observation apparatus 1 represented in the embodiment described above, applications to devices assumed to irradiate a sample S with light L0 of different wavelengths or different beam diameters on the same axis as the planar light L1 are particularly meaningful.
Also in such an aperture mask 22B, as illustrated in
Also in such an aperture mask 22C, as illustrated in
As illustrated in
In addition, as in an aperture mask 22E illustrated in
Also in such an aperture mask 22F, in a case in which the opening edge 25A is projected onto a focusing line, a projected portion P of the opening edge 25A on the focusing line K has a linear spread. For this reason, also in the aperture mask 22F, when light L0 that has passed through the opening part 24F is focused by a light focusing element 23, interference fringes due to diffraction in the opening edge 25A can be suppressed from overlapping each other on the focusing line K and being strengthened together. As illustrated in
As a form in which the opening edge 25A has a shape protruding to the outer side of the focusing line K, for example, like an aperture mask 22G illustrated in
In addition, as another form in which the opening edge 25A has a shape protruding to the outer side of the focusing line K, for example, like an aperture mask 22H illustrated in
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- 1 sample observation apparatus
- 6 image acquiring unit (detection unit)
- 21 light source
- 22 (22A to 22H) aperture mask
- 23 light focusing element
- 24 (24A to 24H) opening part
- 25A opening edge
- F1 focusing axis
- F2 non-focusing axis
- K focusing line
- L0 light
- L1 planar light
- P projected portion
- S sample
Claims
1. A light irradiation device comprising:
- a light source configured to output light having coherence;
- a light focusing element optically coupled with the light source and having a focusing axis and a non-focusing axis intersecting with the focusing axis and configured to focus the light on a focusing line so as to generate planar light; and
- an aperture mask having an opening part that limits a part of luminous fluxes of the light transmitted from the light source to the light focusing element, the aperture mask having a long axis and a short axis, the long axis direction of the aperture mask matching a direction along the focusing axis,
- wherein the opening part of the aperture mask has opening edges disposed to extend in a direction along the focusing axis of the light focusing element, and, in a case in which the opening edges are projected onto the focusing line, corresponding projected portions have linear spreads.
2. The light irradiation device according to claim 1, wherein the opening part has an asymmetrical shape with respect to the focusing line.
3. The light irradiation device according to claim 1, wherein the opening edges have shapes protruding to an outer side of the focusing line.
4. The light irradiation device according to claim 1, wherein the opening part has a hexagonal shape.
5. The light irradiation device according to claim 1, wherein the opening part has a trapezoid shape.
6. The light irradiation device according to claim 1, wherein the opening edges have a zigzag shape.
7. The light irradiation device according to claim 1,
- wherein the opening part has a quadrangle shape, and
- wherein the opening edges intersect with the focusing axis at a predetermined angle.
8. The light irradiation device according to claim 1, wherein the light source is a light source that outputs laser light as the light.
9. A sample observation apparatus comprising:
- the light irradiation device according to claim 1; and
- a detector configured to detect observation light generated in a sample in accordance with irradiation of the planar light from the light irradiation device.
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Type: Grant
Filed: Mar 17, 2021
Date of Patent: Nov 12, 2024
Patent Publication Number: 20230176352
Assignee: HAMAMATSU PHOTONICS K.K. (Hamamatsu)
Inventors: Masanori Kobayashi (Hamamatsu), Satoshi Yamamoto (Hamamatsu)
Primary Examiner: Edwin C Gunberg
Assistant Examiner: Mamadou Faye
Application Number: 17/924,160
International Classification: G02B 21/00 (20060101); G01N 21/64 (20060101);